import numpy as np

a = np.arange(20).reshape(4, 5)
print(a)

# 第一行大于2的数
print(a[:1, a[0] > 2])

# 6,13
print(a[[1, 2], [1, 3]])

# 6,8,11,13
print(a[[1, 2], :][:, [1, 3]])
